From the birth of human history, there have been both right-handed and left-handed people on earth. It is estimated that about 85-90 percent of the world’s population is right-handed. And the remaining 10-15 percent of the people are left-handed, but there are some people who are equally skilled in both hands.
One man is always different from another man. Caste, body shape, tone of voice, appearance, etc. have made one person different from another. There are even subtle differences between the identical twins. And one of the different features is who is right-handed and who is left-handed. But there has always been a lot of curiosity among people as to why some people are right-handed and some people are right-handed. We also often wonder at the various works of the left. However, as a result of such curiosity towards leftists, many superstitions and misconceptions have arisen among the people. Even this misconception has forced people to show brutality towards leftists. But whatever it is, there are some scientific explanations behind such human characteristics. In today’s article we will know the scientific explanation behind some people being right-handed and some people being left-handed. I will also know a lot more information and history about left-handed people.
Why are people left-handed?
Scientists have been trying for more than 150 years to find out exactly why people are right-handed or left-handed. However, the reason why 10 percent of the people are left-handed is not yet 100 percent confirmed. But the things that scientists think can play the most role are-
1. Genetic reasons behind being left-handed
Genes carry all kinds of human characteristics. Genes are the bearers and carriers of all kinds of physical or mental characteristics of human beings. Most scientists think that a child can be right-handed or left-handed because of genetics. A single gene may have been passed down from parent to child to determine which hand the child will have. Although scientists have not been able to accurately diagnose exactly which gene is responsible for this feature.
Again, some recent studies suggest that there is only one gene involved in creating left-handed traits. The genetic proposal to explain hand preference states that there are two copies of a gene in the same genetic space, one called the allele of the other. Usually there are two copies of a gene in one location. One of these copies is called the allele of the other. In the case of right-left inequality, an allele is called the D gene. This D comes from the word ‘Dextral’, which means ‘Right’. The other allele is called the C gene. C comes from the word ‘Chance’.
Again, the alleles of a gene have a manifest and a latent. The allele that is manifested is characterized by T, meaning that if the D gene is manifested in a person, he will be right-handed. In the same way, if the C gene is manifested, the person will be left-handed. However, studies have shown that about 50 percent of people are right-handed, despite the presence of the C gene.
If we want to explain this phenomenon of genes more simply, let us discuss another example. Suppose a child’s skin color is black. Again, the skin color of his father and mother is black and fair, respectively. Suppose the gene B is responsible for the black color and the gene d is responsible for the fair complexion. Now that their child’s skin color has turned black, that means the B gene has been demonstrated on the d gene. So the fair features have not been revealed and the black features have been revealed.
In the same way, genes play a role in whether a child is right-handed or left-handed.
2. The theory of natural selection
The right side of the human brain controls the left side of the body and the left side of the brain controls the right side of the body. People whose language is processed in the left brain are right-handed and those whose language is processed in the right brain are left-handed.
Now the question is how it depends on who will be involved with language processing. Yes, here comes the matter of natural selection theory. From time immemorial, people have used various symbols to express their thoughts. Language has evolved over time, then writing. But when we go to write, first the words are processed in our brain, then the signal comes into our hands and we start writing. That is, if words are processed in the left brain, then since the left brain controls the right side of the body, we become accustomed to writing with the right hand, and when words are processed in the right brain, we become accustomed to writing with the left hand.
Studies have shown that boys are more left-handed than girls. According to the researchers, the testosterone hormone in boys has a special effect behind this phenomenon. Since girls do not have this hormone, they are less likely to be left-handed.
4. Fetal development
Some researchers believe that the environmental impact of the fetus during pregnancy is greater than that of genetics. According to them, the environmental factors of the fetus can have more effect on the child being right-handed or left-handed than genetic traits.
Children learn to use their right or left hand by imitating parents and other notable relatives. Although this theory is questionable. For, in the opposite case of this condition, the theory provides no explanation.
6. Genetic mutations
According to some researchers, there is a type of disease called dyslexia in humans. The disease attacks the language processing process of the brain. This disease causes people to be unable to read anything. In other words, the symptoms of dyslexia are the inability of a person to understand the harmony of letters and letters with the spoken language.
We have already seen how the language processing part of the human brain can play a role in becoming right-handed or left-handed. Since dyslexia attacks the language processing part of the brain, this disease may also be responsible for the right and left skills of humans.
A gene called PCSK-6 is blamed for dyslexia. Researchers have done a lot of research on whether this particular gene has a role in human right-handedness or left-handedness. According to them, the PCSK-6 gene alone cannot be blamed for human right-left inequality. There may be some more genes associated with it.
Researchers have found a correlation between the PCSK-6 gene and right-left asymmetry. Since each gene has two alleles, they have two chances of mutation. The researchers found that patients with dyslexia had the most alternatives to the PCSK-6 gene, meaning that they had mutated the gene once or twice. And in the case of these patients, it has been seen that almost all of them are right-handed.
The research team was convinced that the PCSK-6 gene was directly related to the right-left asymmetry. But they weren’t sure why it only occurs in dyslexic patients. So the team included more than 2,600 people in their study who did not have dyslexia. And it is in this study that they can understand that the PCSK-6 gene is not the only one responsible, there are other genes involved.
7. Situs Inversus
Now let us know about one more incident. That is Sitas Inversus. When the genetic process responsible for right-left inequality is disrupted for any reason, some serious physical changes can also occur. For example, the limbs or organs of the right side of the human body can be located on the left side and vice versa. This phenomenon is called Situs Inversus. This is a genetic change that causes many hearts to be located on the right side instead of the left side of the body. If right-left inequality is created as a result of physical inequality, then the role of citus inversus may also have a role. However, this is still a hypothesis and is still being researched
8. Spinal cord
We have been discussing different aspects of the brain for right-left inequality for so long. However, according to some modern studies, this is a complete denial of our conventional thinking. As modern researchers say, it is not the human brain but the spinal cord that is responsible for being right-handed or left-handed.
The movement of human hands and feet is regulated by the motor cortex region of the brain. Stimulation is created in the brain when we want to move our hands or feet. This stimulation sends the motor cortex first to the spinal cord. The spinal cord then converts this signal into muscle conduction and as a result our arms or legs move.
Examination of pregnant mothers by ultrasonography revealed that the tendency to suck on the hands of the baby was seen after about 13 weeks of gestation. In other words, this right-left inequality is created from the time a person is in the womb of the mother. These tests show that a child sucks the right hand, a child sucks the left hand.
But the problem is that before 15 weeks, there is no connection between the motor cortex and the spinal cord of the human brain. Then, of course, right-left inequality in a 13-week-old baby certainly does not control the human brain.
This means that since the spinal cord controls the movement of our arm or leg muscles, it is not the brain but the spinal cord that is responsible for such right-left asymmetry during pregnancy. Behind this, of course, are the genetic characteristics of the spinal cord. Right-left asymmetry is caused by the activity of genes in the spinal cord. That is, according to their research, it is not the brain but the genetic characteristics of the spinal cord that play a key role in right-handedness or left-handedness.
Ambidextrous or Omniscient
In addition to right-handed or left-handed, there is a type of person who is equally skilled in both hands.
People with such right-left inequality are called ‘Ambidextrous’. This is a very rare occurrence, as less than 1 percent of people have this feature. However, according to many researchers, it is possible to be self-sufficient through practice. If one wants to be equally proficient in both his hands and can practice continuously then one day he will be able to acquire this skill. Since there are very few people around us, we don’t see them all the time. But if you have such a feature, then you are 1 in 1 percent of the world’s people.
Left-handed people have to face all those problems
Since the number of people accustomed to working with the right hand is much higher, almost everything is determined in a way that benefits the right hand. As a result, in all these cases, the leftists have to face various problems and obstacles. E.g.
1. There are various tools including scissors that are designed to be used with the right hand. And left-handed people have to get enough speed to use these tools.
2. The handwriting of most languages, including Bengali, moves from left to right. Of particular note are the languages of the Latin or Indo-European flora. When a left-hander writes in these languages, he has to exercise his hands a lot.
3. When left-handed children start learning to write, in many cases they start writing from the opposite direction. This problem of children is called ‘mirror writing’. Of course this is a natural phenomenon and gradually gets better.
4. According to some studies, diseases like epilepsy and autism are more common in left-handed elephants. However, this is just a statistic for which no scientific evidence has yet been found.
5. You will notice in different test centers that the chairs are made like the writing of right-handed people. You can understand how difficult it would be for a left-handed person to write in these seats.
6. Left-handed people have to face a lot of difficulties in learning to play various instruments including guitar and violin. Since in most cases the teacher is right-handed, everything has to be done very quickly, including first listening, understanding, seeing what the teacher says and then reversing it from right-handed to left-handed, which is undoubtedly difficult enough for new students.
Leftists have to face many more such problems. Of course, let us know the reason. Since the right hand has dominated since ancient times, everything has been done for their convenience.